1.3 Research progress on flavor substances in braised meat
The flavor substance is one of the important indicators for the research and evaluation of soy sauce products. The reason why soy sauce products can stand still in the tide of the times and are deeply loved by people today is inseparable from their unique flavor. In the heating process, precursor substances such as proteins and fat extracts produce flavor substances through lipid oxidation, Maillard reaction and thermal degradation of other substances, thus giving the braised meat a rich taste and volatile flavor substances. The volatile and non-volatile flavor substances are generated by heating different kinds of meat. Jie Sun and others used two different extraction methods to extract the flavor substances in traditional beef jerky, and used gas chromatography-mass spectrometry (GC-MS) to detect the extracts, and finally identified 84 kinds of volatile flavor substances, of which Aldehydes, ethers and certain heterocyclic substances may play a decisive role in the formation of its characteristic flavor. Calkins and others expounded the flavor substances, volatile flavor substances and the taste mechanism of various flavors of beef by referring to the literature. Machiels and others optimized the extraction process by using different extraction heads to extract flavor substances in boiled beef, and identified more than 200 flavor substances, of which 36 were key aroma compositions. Liu and others used gas chromatography-mass spectrometry (GC-MS) to analyze the volatile flavor substances in duck, and found that neutral and alkaline flavor substances may be the main composition of the flavor of duck, while aldehydes and ketones are the main compositions of flavor duck fat. Mahinda and others used gas chromatography-mass spectrometry (GCMS) to study the volatile flavor substances of chicken, beef, and pork by-product mixtures and compared them with cooked chicken white muscle, beef and pork shoulders. Yongxia Xu and others used gas chromatography-mass spectrometry (GC-MS) and gas chromatography odor detector (GC-O) to extract and analyze volatile flavor substances in pork soup, and concluded that 42 volatile flavor substances were identified by GC-MS methods, such as aldehydes, ketones, ethers, hydrocarbons and furans; 19 aroma substances were identified by GC-O methods. Suolian Wu and others used high-performance liquid chromatography and amino acid automatic analyzer to study the flavor substances generated in the process of braised roast chicken. Xue Song and others used electronic nose and electronic tongue technology to evaluate the flavor and quality of Jinhua ham and Xuanwei ham.
 
1.4 Existing problems
At present, there are two main problems with braised meat on the market. One is the preservation of meat, and the other is the difficulty in standardizing the doneness. There are many standards for the control of the heat in the traditional processes. First, the raw meat must be pre-cooked, and it must be slowly cooked in cold water by a cooker. In this process, the muscle protein is slowly denatured by heat, and the blood in the muscle gap is released through a contraction. The smell can be removed from the raw meat. In the heating process, cold water cannot be added twice, which will cause the surface of the raw meat to shrink rapidly, seal the blood and water that has not been removed from the meat, and aggravate the smell of the meat. The pre-cooked meat is added to the stewed soup, and the heat is very difficult to control. If the heating temperature is too high, the outer muscles will contract seriously, which will affect the taste of the meat, such as uneven taste and being short of the flavor of meat. When simmering, although it is convenient for the material exchange between the meat and the soup, the product is prone to overcooked taste. The broth is too thick; it takes a long time and the yield is low. The traditional braised soup cooking process is very dependent on the experience of the cook. The time and heat should be determined according to the type and volume of the raw meat, and it should be adjusted according to the situation.
 
Carrying out industrial standardization research on the main types of soy sauce and braised products, designing temperature-controlled kitchen utensils, and refining processing steps will help standardize the quality of the meat. In the industrial production of braised meat, the problems of excessive microorganisms and preservation cannot be ignored. There are many reasons for causing health and safety, which may be caused by unsanitary transportation routes, production workshops, inappropriate sterilization methods and packaging methods. To deal with the problem of not meeting the standard, you can start from the following aspects: In terms of selecting the plant site, an environment free of pollutants, wastes, and hazardous substances should be preferred, and the plant area should be kept clean; a sanitation management system should be strictly established, and the sanitary production area should be isolated from other areas. The construction of the factory should use environmentally friendly, non-toxic and non-polluting building materials. In the design structure, it is necessary to consider the formation of water vapor in the cooking process so as to avoid the condensed water that accumulates in the ceiling design and contaminates the products. In the production process, the production workers should strictly abide by the sanitation system, regularly clean the equipment, accurately check the sanitation of raw materials, and strictly review the relevant sanitation and safety certificates of raw materials. In terms of sterilization insurance, vacuum packaging, appropriate addition of additives and physical sterilization techniques can be used to extend the shelf life.